Calcium carbide is used as a sulfur scavenger in the refining of metals and metal alloys, particularly in the refining of iron because too high a sulfur content results in brittle steel. Presently, calcium carbide is introduced into the molten metal or metal alloy in granular or powdered form by, in some instances, literally shoveling the loose granules into the molten mass. This method has not been found to be satisfactory, as the exposed granules lose their effectiveness in the open atmosphere, especially at high humidity. Exposure of the calcium carbide granules to humidity results in the production of lime and acetylene, thereby rendering the calcium carbide useless for its intended purpose.
Another problem encountered is that of obtaining the desired dispersion of the relatively low density granular material in the relatively high density molten metals. Thus, when granular calcium carbide is introduced into molten metals in loose form, the granules tend to float on the surface of the molten metal, resulting in only localized concentration of the granules thereby rendering the granular calcium carbide inefficient or ineffective.
One attempt to overcome this problem of proper dispersion has been by packing the granular calcium carbide in steel drums and then maintaining the drums submerged in the molten mass which is usually at a temperature in excess of 1370.degree. C. When the steel drums melt, the granules are released into the molten mass. However, the steel drums melt quickly and suddenly release the granules, which, rather than being dispersed in the molten metal, tend to rapidly rise to the surface where they become mixed with the slag and therefore are only partially able to scavenge sulfur.
Another attempt to overcome this dispersion problem has been by blowing the granular or powdered calcium carbide into the lower levels of the molten mass by means of compressed gas. However, this technique is also not satisfactory due to the buoyancy effect of the granules and the tendency of the granules to clog the inlets through which they are blown into the molten mass necessitating frequent clearing of these inlets.
Although it is only remotely related to the invention described herein, it should be pointed out that it is known to mold non-metallic powders such as those used in ceramics into a solid mass by combining the non-metallic powder with an organic, heat fugitive agent such as a polymer resin that is depolymerizable or decomposable upon being subjected to heat. Upon heating, the polymer resin vaporizes out of the non-metallic material to obtain a vitrified article of desired shape comprising the non-metallic powder as disclosed in U.S. Pat. No. 2,593,507.
It would be desirable, therefore, to provide a means whereby granular or powdered calcium carbide or other suitable sulfur scavengers, could be introduced into molten metals in a manner that would enable the calcium carbide to be properly dispersed so that it could effectively and efficiently perform its intended function. It would also be desirable to provide granular or powdered calcium carbide in a form that would greatly reduce, if not eliminate, the effects of high humidity atmospheres on said granules.